Surgical saw with sensing technology for determining cut through of bone and depth of the saw blade during surgery

ABSTRACT

Sensing technology methods related thereto for determining cut through of bone and a depth of penetration of a working portion of a surgical instrument (e.g., an oscillating saw blade in a cut). A first sensor outputs a first signal representative of a displacement of the cutting edge of the saw blade in the cut. A second sensor outputs a second signal representative of a force applied to the cutting edge of the saw blade. As such, monitoring the first and/or second sensor may allow for the saw to be stopped upon completion of a cut (e.g., when the saw passes completely through a medium to be cut or upon reaching a predetermined depth for the cut).

RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 14/537,586 filed Nov. 10, 2014, entitled “SURGICAL SAW WITHSENSING TECHNOLOGY FOR DETERMINING CUT THROUGH OF BONE AND DEPTH OF THESAW BLADE DURING SURGERY,” which claims the benefit of U.S. ProvisionalApplication No. 61/902,002 filed Nov. 8, 2013, entitled “SURGICAL SAWWITH SENSING TECHNOLOGY FOR DETERMINING CUT THROUGH OF BONE AND DEPTH OFTHE SAW BLADE DURING SURGERY,” the contents of which are incorporated byreference herein as if set forth in full.

BACKGROUND

Orthopedic sawing procedures may result in incorrect saw lengths ordamage to a patient (i.e., if the sawing action continues after cutcompletion or if an incorrect cut depth is made), which can lead tosurgical complications. Furthermore, in cases where the length of a cutmade using a surgical saw is to be determined, determining the lengthfor a cut can be a time consuming procedure which is undesirable whentissue is exposed and potentially subjected to infection.

As shown in FIG. 1, a cross section of a bone 10 having with a hardcortex 12 is shown. The bone 10 may be surrounded by a medium 14 that isless dense than the hard cortex 12 (e.g., soft tissue or air in the caseof a bone exposed during a surgical procedure). In orthopedicprocedures, it may be necessary to saw a bone 10 (e.g., saw a portion ofa bone or completely through a bone). When cutting through all or aportion of a bone 10, failure to arrest oscillation of the saw blade assoon as a cut is complete may result in unnecessary damage to the areaaround the cut. Furthermore, precise control over the depth of a cut maybe needed in certain surgical operations.

Previously proposed techniques for sawing include the surgeon making acut through the bone until the surgeon “feels” the saw blade passcompletely through the bony structure or have the surgeon estimate adepth of the cut during the cutting operation. That is, the surgeon mustrely on his or her senses and judgment alone to determine when the sawblade has passed completely through the bony structure or to apredetermined depth. Once the surgeon believes that he or she has passedcompletely through the structure or to the predetermined depth, the sawblade oscillation is arrested by the surgeon. Thereafter the surgeon maymeasure the length of the cut. A possible resulting complication of thisprocedure is that the surgeon may mistakenly “feel” the saw blade passthrough a layer of differing density, thus falsely believing the cut tobe complete. Additionally, the surgeon may not precisely “feel” the sawblade pass through the bone, thereby possibly damaging tissue on theopposite side of the bone.

Additionally, it may be necessary of a surgeon to measure the cut lengthonce the cut is complete or stop cutting at a prescribed length that waspredetermined by imaging software or a measurement jig. However, accessto the anatomy that is cut may be limited, thus also limiting theability to use such measurement jigs or other fixtures to control thedepth of a cut. As such, traditional measurement techniques forverification of the cut length may be subject to error. As such, theprocess of sawing to a measured depth often includes inaccurate guesswork. Conservative sawing may result in incomplete sawing (i.e., failureto saw completely through the bone or failure to saw to a predetermineddepth), thus requiring multiple attempts. As such, sawing to apredefined depth is quite difficult. Additionally, it may be difficultto quickly arrest the saw blade motion upon cut completion. As such, theprocess may consume a substantial amount of surgical time resulting in alarge cost per patient. By combining the sawing and depth measurementprocess into one accurate procedure, cost is reduced along with adecrease in patient morbidity.

SUMMARY

The present disclosure relates generally to systems, methods, andapparatuses for use in connection with determining when an instrumentworking portion (e.g., a cutting edge of a surgical saw) has completed adesired cut (i.e., has completed a cut of a certain length that maycorrespond to completely through a bone or partially through a bone).More specifically, the present disclosure presents embodiments relatedto a system and method for determining the length of a cut made througha bone of a patient without removing the saw blade from the cut formedin the bone. As such, in at least some embodiments herein, a saw isdisclosed that automatically cease a cutting operation upon passingcompletely through a bone. Also, embodiments of a saw that automaticallyarrests a sawing action upon achieving a predetermined depth of cut aredescribed. The present disclosure may thus include embodiments thatallow for a saw blade to cut through a bone to a predetermined depth(e.g. measured from a portion of the bone or a cutting guide).Accordingly, the present disclosure may find application in the field ofsurgical sawing where the depth of the cut made in a bone is to bedetermined.

The present disclosure also includes embodiments of saw blade assembliesthat may be specifically adapted for use for saw blade penetrationmeasurement. Accordingly, the saw blade assemblies and saws disclosedherein may provide increased efficiency, reliability, and accuracy inrelation to a saw blade penetration measurement system. For instance, incertain embodiments, a saw blade assembly may be used in conjunctionwith a saw as described herein to provide an improved platform tofacilitate measurement of a cut created by the saw using a saw bladepenetration measurement system without having to remove the saw bladefrom the cut during operation.

Systems for drill bit penetration measurement systems have been proposedsuch as described in U.S. Pat. No. 6,665,948, the entirety of which isincorporated herein by reference. In this regard, the descriptionpresented herein may provide adaptations, refinements, and/or additionalfeatures for use in connection with a saw blade penetration measurementsystem. As such, the present disclosure may facilitate improvements inthe efficiency, accuracy, and or ergonomics of prior approaches tosurgical saws.

Accordingly, a first aspect includes a saw blade assembly for use with asaw having a displacement sensor for outputting a signal representativeof a displacement of the saw blade with respect to a reference point.The assembly includes a saw blade, a bushing, and an engagement memberdisposed on the bushing. The saw blade may include a cutting edgedisposed at a distal end of the saw blade. Alternatively, the saw blademay include a cutting edge that extends along a length of the saw blade(e.g., along a majority or substantially all of the saw blade). The sawblade may include a shank that is adapted for engagement with a driveassembly that provides an oscillating motion of the saw blade duringoperation. The bushing may engage at least a portion of the saw blade orshank (e.g., through an aperture in the bushing or the saw blade). Assuch, the bushing may be constrainedly moveable relative to the blade orshank in a direction along a cutting direction of the saw blade. Theengagement member is adapted for engagement with a displacement sensingarm of the displacement sensor. In this regard, the engagement member isengageable with the displacement sensing arm for corresponding movementbetween the bushing and the displacement sensing arm.

A number of feature refinements and additional features are applicableto the first aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thefirst aspect.

For example, in an embodiment, an aperture may be provided at thebushing that may define an opening extending from a distal end of thebushing to a proximal end of the bushing. In this case, the distal endof the opening may comprise a reference surface. The reference surfacemay extend at least partially along a portion of the saw blade whendisposed in the aperture. In other embodiments, the bushing may beconformably shaped relative to the body of the saw blade to facilitatethe constrained movement relative to the oscillation of the blade. Insuch embodiments, the bushing may or may not extend about entirety ofthe shank. For example, the bushing may include a dished or concavesurface that is alignable with the body or shank of the saw blade forconstrained movement in a direction along the sawing axis. In anyregard, the saw blade may be moved relative to the reference surfacewhen making a cut in a medium so that the displacement between the sawblade and the bushing may be measured.

In any regard, the bushing may be disposable adjacent to the cuttingedge of the saw blade (i.e., adjacent to the distal end of the sawblade). Accordingly, the reference surface may be alignable with thecutting edge of the saw blade to define a reference point from whichdisplacement of the saw blade may be measured when making a cut usingthe saw blade. In this regard, the displacement sensing arm to which thebushing is engageable may be operatively engaged with a displacementsensor of a saw as will be described in greater detail below. In thisregard, the saw blade may be advanceable relative to a medium to be cutto create a cut such that the cutting edge of the saw blade is displacedrelative to the reference surface upon the advancement of the saw bladeinto the cut. Accordingly, when the engagement member operativelyengages a displacement sensing arm of a displacement sensor, thedisplacement sensor may measure the displacement of the cutting edgefrom the reference surface.

In an embodiment, the reference surface may contact a peripheral portionextending about the cut (e.g., on at least a first side of the cut) uponadvancement of the saw blade to create the cut. The bushing may beengageable against the peripheral portion extending about the cut so asto maintain the reference point stationary against the peripheralportion of the cut in a cutting direction. For instance, the bushing maybe biased toward the distal end of the saw blade (e.g., under theinfluence of the displacement sensing arm or by another biasing memberdisposed relative to the saw blade and the bushing). In this regard, asthe reference surface of the bushing may be maintained adjacent to thesurface to be sawed, the accuracy of the displacement measure uponadvancement of the saw blade may be improved given the proximity ofcontact of the bushing defining the reference surface relative to thelocation of the cut.

In various embodiments, the engagement member may include anyappropriate mechanism for attachably connecting the bushing to adisplacement sensing arm. In one particular embodiment, the engagementmember may include a post extending from the bushing that is selectivelyengageable with the displacement sensing arm of the displacement sensor.In this regard, the post may facilitate relative pivotal movementbetween the post of the bushing and the displacement sensing arm (e.g.,prior to engagement of the shank with the saw). Further still, thebushing may include a snap interface that engages the displacementsensing arm. As such, the snap interface may include fingers thatsnappingly engage the displacement sensing arm (e.g., at a configureddistal portion thereof that is shaped to correspond to the fingers ofthe bushing). That is, the bushing may be snapped to a portion of thedisplacement sensing arm. In any regard, movement that engages thebushing with the displacement sensing arm may allow for improvedergonomics when engaging the saw blade assembly with a saw by allowingthe shank to be aligned with the saw after engagement of the bushingwith the displacement sensing arm.

In another embodiment, the saw may not include a bushing, but the bladeor saw is received, guided or supported by a cutting guide or jig. Thecutting guide or jig guides the saw blade or the saw along a sawingaxis. A displacement sensor using the cutting guide or jig as areference surface for measuring cutting depth may be provided where thedisplacement sensor may be in contact with a stationary portion of thecutting guide as the saw blade is advanced through the bone to determinethe depth of a cut made.

In an embodiment, the saw blade assembly may be provided as a one-timeuse, disposable component for use in a surgery or other operation. Inthis regard, the saw blade assembly may include features that helpreduce the likelihood that the saw blade is reused in contradiction ofinstructions regarding one time use. Such features may at least reducethe functionality of the saw blade assembly (e.g., potentially to thepoint where the saw blade assembly is incapable of reuse with themeasurement system). For example, in an embodiment, the shank mayinclude a destructible portion that is at least partially destructibleduring a cleaning process. Additionally or alternatively, the bushing(e.g., the engagement portion of the bushing) may comprise adestructible portion that, when destroyed, limits or prevents reuse withthe measurement system. In this regard, the bushing or a portion thereof(e.g., an engagement portion) may be destroyed during a cleaning processto avoid reuse of the blade after cleaning. In one particularembodiment, the destructible portion may be meltable. As such, a meltingtemperature of the destructible portion may be greater than an operatingtemperature of the saw blade and less than an autoclave temperature. Assuch, the destructible portion may remain intact during operation of thesaw blade assembly. However, upon undergoing a cleaning or sterilizationprocess (e.g., autoclaving), the destructible portion may be at leastpartially degraded. In one embodiment, the melting temperature of thedestructible portion is not less than about 60° C. and not greater thanabout 110° C. The destructible portion may also be destroyed uponexposure to a cleaning or sanitizing chemical or the like used in thecleaning process (e.g., as an alternative to or in addition to beingmeltable).

In view of the foregoing, the destruction of the destructible portionmay alter the shape of the shank of the saw blade or the bushing suchthat engagement with a saw or a measurement system thereof may be atleast partially prevented or degraded. For instance, the destructibleportion may be used to at least partially establish registration betweenthe shank and a chuck of the saw. Accordingly, upon destruction of thedestructible portion, registration between the saw blade assembly andthe chuck of the saw may be reduced (e.g., potentially to the point ofinoperability of the saw blade). For example, the destructible portionmay include a proximal end portion of the shank. In this regard, thedestructible portion may include at least a portion of an engagementfeature for engagement of the shank by the chuck. In an embodiment, thedestructible portion may include at least a portion of at least onesidewall of the shank. Additionally or alternatively, the engagementfeature may include a detent engageable by an engagement member in thechuck. As such, the destructible portion, after having been exposed to acleaning process, may not be registerable with respect to assembly chuckof the saw. That is, the surface area of the engagement feature of theshank that is in contact with the chuck when the saw blade is engagedwith the chuck may be at least reduced upon exposure of the destructibleportion to a cleaning process. Further still, as the destructibleportion may comprise at least a portion of the bushing, the bushing maybe degraded in a cleaning process such that destruction of thedestructible portion results in the bushing not being engageable withthe displacement sensing arm.

A second aspect includes a method for use of a saw blade assembly with asaw having a displacement sensor for outputting a signal representativeof a displacement of a cutting edge of the saw blade assembly withrespect to a reference point. The method may include engaging adisplacement sensing arm of the displacement sensor with an engagementmember of a bushing. The bushing may be constrainedly moveable relativeto a saw blade along a cutting direction of the saw blade during sawing.The engaging may result in corresponding movement of the bushing and thedisplacement sensing arm. The method may include aligning a shank of thesaw blade with a chuck of the saw and securing the shank with the chuckof the saw to restrict movement between the saw blade and the motorassembly.

A number of feature refinements and additional features are applicableto the second aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thesecond aspect. For example, in an embodiment, the saw blade assembly maybe provided in accord with any of the features and/or featurerefinements described above in connection with the first aspect.

For example, in an embodiment, the method may include positioning adistal portion of the bushing adjacent to a cutting edge of the sawblade (e.g., at a distal portion thereof). In this regard, the methodmay also include contacting the cutting edge of the saw blade to asurface of a medium to be sawed. Accordingly, the distal portion of thebushing may contact the surface of the medium to be sawed. As such, themethod may also include establishing the reference point when thecutting edge of the saw blade and the distal portion of the bushing arein contact with the surface of the medium to be sawed. The method mayalso include advancing the saw blade into the medium to be sawed, suchthat the cutting edge advances in relation to the distal portion of thebushing in contact with the surface of the medium to be sawed. Thus, themethod may include producing relative movement of the displacementsensing arm relative to the displacement sensor upon advancing the sawblade into the medium. As the displacement sensing arm may beoperatively engaged with the displacement sensor, the method may furtherinclude outputting a signal from the displacement sensor indicative ofthe amount of displacement of the cutting edge of the saw blade relativeto the distal portion of the bushing. In other embodiments, the saw mayinclude a displacement sensing arm in direct contact with a medium to becut or a cutting guide disposed stationary relative to a medium to becut. In this regard, relative motion between the saw blade and themedium to be cut may be measured by the displacement sensing arm.

A third aspect includes a saw blade assembly for use in a medical sawfor single use applications. The saw blade assembly includes a saw bladewith a cutting edge and a shank. The assembly also includes a bushing.The saw blade assembly includes a destructible portion. The cutting edgeis disposed at a distal end of the saw blade. The shank is disposedadjacent to a proximal end of the saw blade, and a blade body memberextends along a length of the saw blade between the distal end and theproximal end. The shank and/or bushing may include the destructibleportion that is at least partially destructible during a cleaningprocess. The bushing may be at least partially captured by the shanksuch that the bushing is non-removably engaged with the shank when thedestructible portion is intact. Upon destruction of the destructibleportion, the bushing may no longer be engaged with the shank and/or anengagement portion may be destroyed, thus preventing engagement with thedisplacement sensing arm upon destruction of the destructible portion.

A number of feature refinements and additional features are applicableto the third aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thethird aspect or any of the other aspects disclosed herein.

For example, in an embodiment, the destructible portion may be meltable.In this regard, a melting temperature of the destructible portion may begreater than an operating temperature of the saw blade and less than anautoclave temperature. For instance, the melting temperature of thedestructible portion may be not less than about 60° C. and not greaterthan about 110° C. Additionally, as referenced above in connection withthe first aspect, the destructible portion may be destroyed uponexposure to a cleaning or sanitizing chemical or the like used during acleaning and/or sanitizing process.

As described above with respect to the first aspect, the destructibleportion may comprise a proximal end portion of the shank. Thus, upondestruction of the destructible portion, at least a portion of the shankmay undergo a change in shape. Accordingly, the destructible portion mayinclude at least a portion of an engagement feature for engagement ofthe shank by a chuck of a saw. For instance, the destructible portionmay include at least a portion of at least one sidewall of the shank.Additionally or alternatively, the engagement feature may include adetent engageable by the chuck (e.g., the detent features may correspondwith a quick-change style chuck device where the detents are used toselectively retain the shank in the chuck device). Further still, thedestructible portion, after destruction thereof, may prevent engagementof the bushing with the displacement sensing arm and/or may destroyengagement between the saw blade and the bushing.

Accordingly, in an embodiment, the destructible portion, after havingbeen exposed to a cleaning process, may not be registerable with respectto the chuck device. In this regard, the surface area of the sidewall ofthe shank may be at least reduced upon exposure of the destructibleportion to a cleaning process (e.g., an autoclave process or a chemicalsanitation process).

A fourth aspect includes a method for a saw blade assembly for use in amedical saw for single use applications. The method includes exposingthe saw blade assembly to a cleaning process and degrading at least aportion of a destructible portion. For example, the destructible portionmay comprise a portion of the shank and/or a portion of a bushingprovided with the saw blade assembly. In either case, the destructibleportion may be degraded in response to the exposing such that the sawblade assembly is not functional after the degrading. Additionally, anumber of feature refinements and additional features are applicable tothe fourth aspect. These feature refinements and additional features maybe used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of any ofthe aspects discussed herein.

For instance, in an embodiment the exposing may include autoclaving thesaw blade. As such, the degrading may include melting at least a portionof the destructible portion in response to the autoclaving. The meltingmay occur at a temperature of not less than about 60° C. and not greaterthan about 110° C. In this regard, the destructible portion maywithstand temperatures associated with normal operation of the sawblade, but may be degraded (i.e., melted) upon exposure to theautoclaving process. In another embodiment, the exposing may includeapplying a cleaning chemical to the saw blade such that the degradingincludes removal of at least a portion of the destructible portion inresponse to applying the cleaning chemical.

As described above, in an embodiment the degrading may result inchanging a shape of a shank of the saw blade. Thus, the degrading mayinclude removing at least a portion of the destructible portion at ashank of the saw blade. The portion of the destructible portion removedmay at least be a portion of an engagement feature for engagement of theshank by a chuck device of a saw. For instance, the destructible portionmay include at least a portion of at least one sidewall of the shank ormay include a detent engageable by the chuck device. In any regard, thedegrading may result in reducing the registration of the shank withrespect to a chuck device of a saw. Additionally or alternatively, aportion (e.g., an engagement portion) of a bushing of the saw bladeassembly may comprise the destructible portion that is degraded toprevent the bushing from engaging with a displacement sensing arm.

A fifth aspect includes a saw including a saw blade penetrationmeasuring system for determining, with respect to a reference point, adepth of penetration of a cutting edge of a saw blade in a cut. The sawincludes a chuck for engagement with a shank of a saw blade. The chuckis operable to constrain a saw blade engaged by the chuck during sawing.The saw also includes a displacement sensing arm extending from the sawthat may be engageable with a bushing member that is constrainedlymoveable with respect to a saw blade engaged by the chuck. The saw alsoincludes a displacement sensor disposed in a fixed relative positionwith respect to a saw blade engaged by the chuck. The displacementsensor is adapted for relative movement with respect to the displacementsensing arm. Accordingly, the displacement sensor is operative to outputa first signal representative of the displacement of the sensing armrelative to the displacement sensor. The movement of the displacementsensing arm relative to the saw corresponds to displacement of thebushing relative to a saw blade engaged by the chuck. In this regard,movement of the displacement sensing arm relative to the saw and thecorresponding movement of the saw blade relative to the bushing may bemeasured as an output of the displacement sensor of the saw.

A number of feature refinements and additional features are applicableto the fifth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thefifth aspect. Furthermore, any of the features discussed in relation toany other aspect discussed herein may be used with the fifth aspect.

For example, in an embodiment, the displacement sensor may be disposedinternally to a saw housing and the displacement sensing arm may extendfrom the saw housing. Accordingly, the displacement sensing arm mayextend from the saw housing. As such, at least a portion of thedisplacement sensing arm (e.g., a proximal portion thereof) may extendtowards a saw blade engaged by the chuck. In an embodiment, thedisplacement sensing arm may include a hole engageable with a post ofthe bushing to effectuate corresponding movement of the displacementsensing arm and the bushing. In another embodiment, the bushing may havea snap interface such that a portion of the bushing snaps about aportion of the displacement sensing arm to engage therewith.

In an embodiment, the displacement sensor may include a linear variabledifferential displacement transducer (LVDT). Accordingly, a coil of theLVDT may be disposed in the housing and the displacement sensing arm mayinclude a moveable core displaceable with respect to the coil of theLVDT. The displacement sensor may have a total measurable travel of atleast about 2.5 inches (6.4 cm). However, any other appropriate type ofdisplacement sensor (e.g., a relative or absolute position sensor) maybe used such as, for example, an optical sensor or the like.Furthermore, other appropriate types of sensors or sensor systems may beemployed including digital encoders, laser sensors, 3D triangulationbased on imaging and fiducial markings, etc.

In an embodiment, the displacement sensing arm may be biased to a distalposition relative to a saw blade engaged by the chuck. Additionally oralternatively, the displacement sensing arm may be selectively removablefrom the saw housing. Further still, the displacement sensing arm may beselectively retainable in a proximal position. The displacement sensingarm may be selectively removable from a passage extending through thesaw housing, such that the passageway is selectively opened from aproximal end thereof to a distal end thereof (e.g., by removal of thedisplacement sensing arm and/or removal of an end cap or the like).

In an embodiment, the chuck of the saw may include a removable assemblyengaged to a drive motor by way of a coupling receiver. The removableassembly may be attached to the saw by way of a release mechanism. Assuch, the chuck may be selectively removable from the saw.

In an embodiment, the saw may include a light emitter operable to emitlight in a direction toward the saw blade retained by the chuck.

A sixth aspect includes a method for use of a saw including a saw bladepenetration measuring system for determining, with respect to areference point, a depth of penetration of cutting edge of a saw bladein a cut. The method includes engaging a shank of a saw blade with achuck of the saw. The method also includes constraining the saw bladeengaged by the chuck to limit relative axial movement between the sawand saw blade during sawing. The method further includes connecting adisplacement sensing arm extending from the saw to a bushing member thatis constrainedly moveable with respect to the saw blade engaged with thechuck.

A number of feature refinements and additional features are applicableto the sixth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thesixth aspect. Furthermore, any of the features discussed in relation toany other aspect discussed herein may be used with the sixth aspect.

For example, the method may also include aligning a distal edge of thebushing with a cutting edge of the saw blade and moving the displacementsensing arm relative to a displacement sensor of the saw. However, inother embodiments, the displacement sensing arm may contact a cuttingguide to establish a reference point. In any regard, the method mayinclude establishing the reference point relative to the cutting edge ofthe saw blade. Furthermore, the method may include oscillating the sawblade to create a cut to advance the saw blade in the cut and detectinga relative movement of the saw blade relative to the reference point byway of corresponding movement of the displacement sensing arm relativeto the displacement sensor. As such, a displacement may be measured. Thesaw may be stopped automatically in response to completion of a cut(i.e., sawing through a bone or the like) which may be determined uponmonitoring a displacement sensor and/or a force sensor. Furthermore, apredetermined displacement may be set such that the saw may be stoppedupon displacement of the saw blade to the predetermined displacementlength. The method may include biasing the displacement sensing arm to adistal position, wherein the biasing maintains the distal edge of thebushing in contact with a medium into which the saw blade is advanced tocreate the cut.

A seventh aspect includes a saw including a saw blade penetrationmeasurement system for determining, with respect to a reference point, adepth of a penetration of a cutting edge of a saw blade in a cut along acutting axis when the cutting edge of the saw blade passes from a firstmedium to a second medium, the first medium contiguous with the secondmedium, the first medium having a first density, the second mediumhaving a second density. The saw includes a first sensor outputting afirst signal representative of a displacement, with respect to thereference point, of the cutting edge of the saw blade in the cut and asecond sensor outputting a second signal representative of a forceapplied to the cutting edge of the saw blade. The saw also includes achuck engageable with the saw blade. Accordingly, movement isconstrained between the chuck and the saw blade. The saw also includes amotor that is operatively engaged with the chuck to oscillate the sawblade. The saw also includes a processor in electrical communicationwith the first and second sensors. The processor is configured in afirst mode to output a third signal representative of the depth ofpenetration of the cutting edge of the saw blade when the cutting edgeof the saw blade passes from the first medium to the second medium. Thethird signal may be based on the first and second signals.

A number of feature refinements and additional features are applicableto the seventh aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of theseventh aspect. For example, any of the forgoing features described withrespect to any other aspect disclosed herein may be utilized with theseventh aspect.

For example, in an embodiment the first sensor may include a linearvariable differential displacement transducer (LVDT), a digital encoder,an optical displacement sensor, or any other appropriate displacementsensor. In an embodiment, the second sensor includes a load cell. Thethird signal may be output when a second time derivative of the firstsignal is greater than zero and a first time derivative of the secondsignal is less than zero.

In an embodiment, the first sensor may be a linear variable differentialdisplacement transducer (LVDT), the second sensor may be a load cell,and the third signal may be output when the second time derivative ofthe first signal is greater than zero and a first time derivative of thesecond signal is less than zero. That is, upon passing fully through thebone, the saw may undergo a decrease in force applied to the cuttingedge and accelerate when the cut is complete. That is, monitoring thefirst and second sensor for this occurrence may allow the saw to bestopped upon completion of a cut. In an embodiment, the bone surroundedby a second medium with a density less than the bone such that uponcompletion of the cut the saw experiences the decrease in force againstthe cutting edge and acceleration of the blade.

In an embodiment, the system may include a mode selector and theprocessor may be configured to operate in a mode selected from the groupof modes consisting of the first mode wherein the third signalcorresponds to completely cutting through a structure and a second mode,wherein the processor is configured such that the third signalcorresponds to when the saw blade has reached a predetermined depth forthe cut. The first sensor may be a linear variable differentialdisplacement transducer, the second sensor may be a load sensor, and theprocessor, in the first mode, outputs the third signal when a secondtime derivative of the first signal is greater than zero and a firsttime derivative of the second signal is less than zero, thus indicatingthe saw has passed through the bone. Also, the processor, in the secondmode may output the third signal in response to the measureddisplacement equaling a predetermined depth.

In an embodiment, the third signal may include an alert perceivable by auser of the saw. The alert may be an auditory alert. Additionally oralternatively, the alert may include a change in speed of the motor ofthe saw. For example, the alert may include stopping the oscillation ofthe motor of the saw.

A eighth aspect includes a surgical instrument that includes aninstrument working portion adapted to engage a portion of a patient toperform a surgical operation. The surgical instrument also includes alight emitter adapted to emit light in a direction toward the patientwhen the instrument working portion is engaged with the portion of thepatient to perform the surgical operation.

A number of feature refinements and additional features are applicableto the eighth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of theeighth aspect. For example, any of the forgoing features described withrespect to any or all of the foregoing aspects may be utilized with theeighth aspect.

For example, in an embodiment, the surgical instrument may correspond toany of the foregoing saw embodiments for determining a depth ofpenetration of a saw blade in a cut. However, in other embodiments, thesurgical instrument may comprise other types of surgical saws, asurgical grinder, a surgical chisel, or some other surgical instrumentwithout limitation.

In an embodiment, the light emitter may include a light emitting diode(LED) light source. For instance, in an embodiment, the light source maybe disposed within a housing of the surgical instrument. Alternatively,the light source may be disposed remotely from the surgical instrumentand transmitted to the light emitter (e.g., by way of fiber optics orthe like).

In an embodiment, the surgical instrument may include a measurementsystem for determining, with respect to a reference point, a depth ofthe instrument working portion when the instrument working portionpasses from a first medium to a second medium. As such, any of theforegoing discussion with respect to embodiments of measurement systemsmay be provided in various embodiments without limitation. For instance,the surgical instrument may include a first sensor outputting a firstsignal representative of a displacement, with respect to the referencepoint, of the instrument working portion, a second sensor outputting asecond signal representative of a force applied to the instrumentworking portion, and a processor in electrical communication with thefirst and second sensors. The processor may be configured in a firstmode to output a third signal representative of the depth of penetrationof the instrument working portion of the surgical instrument when theinstrument working portion passes from the first medium to the secondmedium, the third signal based on the first and second signals.

In an embodiment, the light emitter may be selectively operable betweentwo emitting states (i.e., always on and trigger depression) and anon-emitting state. For instance, the emitting state may occur uponoperation of the instrument working portion, and the non-emitting statemay occur upon cessation of operation of the instrument working portion.Additionally or alternatively, the light emitter may be selectivelychanged between the emitting state and non-emitting state by way of astate switch or the like.

A ninth aspect includes a saw including a saw blade penetrationmeasurement system for determining, with respect to two referencepoints, completion of a cutting operation when the cutting edge of thesaw blade passes from a first medium to a second medium, the firstmedium contiguous with the second medium, the first medium having afirst density, the second medium having a second density. The saw mayinclude first and second sensors for outputting, independently, thedisplacement of the saw blade relative to reference points establishedby each of the first and second sensors. A third sensor outputting athird signal representative of a force applied to the cutting edge ofthe saw blade may also be provided. The saw also includes a chuckengageable with the saw blade. Accordingly, movement is constrainedbetween the chuck and the saw blade. The saw also includes a motor thatis operatively engaged with the chuck to oscillate the saw blade. Thesaw also includes a processor in electrical communication with thefirst, second and third sensors. The processor is configured in a firstmode to output a fourth signal representative of when the cutting edgeof the saw blade passes from the first medium to the second medium basedon at least one of the first, second or third signals (i.e., when thesaw passes completely through a medium to be cut).

A number of feature refinements and additional features are applicableto the ninth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of theninth aspect. For example, any of the forgoing features described withrespect to any other aspect disclosed herein may be utilized with theninth aspect.

Additionally, in an embodiment the first and sensors include a linearvariable differential displacement transducer (LVDT). In an embodiment,the third sensor includes a load cell. The fourth signal may be outputwhen a second time derivative of the first or second signal is greaterthan zero and a first time derivative of the third signal is less thanzero.

In an embodiment, the first and sensors may be a linear variabledifferential displacement transducer (LVDT), the third sensor may be aload cell, and the fourth signal may be output based on the first,second, and/or third sensor outputs (e.g., when the second timederivative of one of the first and second signals is greater than zeroand a first time derivative of the third signal is less than zero). Insome embodiments, absolute values of force and displacement may also beused. In an embodiment, the first medium may be a bone surrounded by thesecond medium (e.g., air or surrounding soft tissue).

The system may include a mode selector and the processor may beconfigured to operate in a mode selected from the group of modesconsisting of the first mode wherein the fourth signal corresponds to acondition when the saw has passed completely through the bone. In asecond mode, the processor is configured such that the fourth signalcorresponds to a when the saw blade has reached a predetermined depth ofthe cut. In this regard, the first and second sensors may be linearvariable differential displacement transducers, the third sensor may bea load sensor, and the processor, in the first mode, outputs the fourthsignal when a second time derivative of one of the first and secondsignals is greater than zero and a first time derivative of the thirdsignal is less than zero. Also, the processor, in the second mode, mayoutput the fourth signal in response to one or both of the first andsecond sensors outputting a signal corresponding to the predetermineddepth.

In an embodiment, an output device presents an alert perceivable by auser of the saw based on the fourth signal. The alert may be an auditoryalert. Additionally or alternatively, the speed of the motor of the sawis changed based on the fourth signal. For example, the oscillation ofthe motor of the saw is stopped based on the fourth signal.

A tenth aspect includes a sawing assembly having a displacement sensorfor performing an automatic disabling of cutting when a predeterminedcutting depth has been determined. The assembly includes a cutting guideor cutting jig, a saw having a blade and a displacement sensor foroutputting a signal representative of a displacement of the saw bladewith respect to a reference point. The saw blade has a cutting edgedisposed at a distal end of the saw blade. The saw blade includes ashank that is adapted for engagement with a drive assembly that providesan oscillating motion of the saw blade. The cutting guide or cutting jigincludes one or more apertures sized to receive at least a portion ofthe saw blade or shank through the aperture. As such, the cutting guideor cutting jig guides the saw blade in a direction along a cuttingdirection of the saw blade.

A number of feature refinements and additional features are applicableto the tenth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of theforegoing features described above may be, but are not required to be,used with any other feature or combination of features of the tenthaspect.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view of a bone illustrating a prior art method ofusing a saw mechanism to create a bicortical path through a corticalbone having multiple layers;

FIG. 2 is an elevation view of an embodiment of a real-time, saw bladepenetration measurement system;

FIG. 3 is an elevation view of an embodiment of a control panel of acontroller assembly of FIG. 2;

FIG. 4 is a schematic block diagram of the controller assembly of FIG. 2and the inputs and outputs of the controller assembly;

FIG. 5 is a diagram illustrating the position of the saw blade of FIG. 2and the corresponding output of the first and second sensors of thedisplacement and load measurement assemblies of FIG. 2;

FIG. 6 is a flow diagram of an embodiment of a method for determiningthe depth of penetration of a saw blade;

FIG. 7 is a flow diagram of an embodiment method for determining thedepth of penetration of a saw blade;

FIGS. 8A and 8B are perspective and side views, respectively, of anembodiment of a saw including a saw blade penetration measurementsystem;

FIG. 9 is a perspective view with a partial cutaway of a saw body of anembodiment of a saw including a saw blade penetration measurementsystem;

FIG. 10 is an elevation view of an embodiment of a bushing for a sawblade penetration measurement system;

FIG. 11 a perspective view of an embodiment of a saw blade with anintact destructible portion;

FIG. 12 is a perspective view of the embodiment of the saw blade of FIG.11, wherein the destructible portion has been at least partiallydestroyed;

FIGS. 13A and 13B depict an embodiment of a controller for use inoperation of a saw having a saw blade penetration measurement system;

FIG. 14 is a cross sectional schematic view of a saw blade that has beenadvanced into a cut in a medium relative to a bushing engaged with adistal portion of a displacement sensing arm;

FIG. 15A is a perspective view of an embodiment of a saw including twosaw blade penetration measurement devices;

FIGS. 15B and 15C are cross sectional schematic views of the saw bladefrom FIG. 15A that has been advanced into a cut in a medium relative totwo bushings engaged with a distal portion of respective displacementsensing arms; and

FIG. 16 is a perspective view with a partial cutaway of a sawingassembly of an embodiment of a saw including a saw blade penetrationmeasurement system and a cutting board/cutting jig;

FIGS. 17A-17C depict various embodiments of surgical instrumentsincluding light emitters.

FIG. 18 is a perspective view of an embodiment of a saw including a sawblade penetration measurement system.

FIG. 19 is a perspective view of the embodiment of FIG. 18 in partialcutaway view to expose internal components of the embodiment of the sawfor illustrative purposes.

FIG. 20 is a cross-sectional view of the saw FIG. 18.

FIGS. 21A-21C depict a progression for engagement of a saw bladeassembly with the saw FIG. 19.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right,” “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” and “outwardly” refer to directions toward and awayfrom, respectively, the geometric center of the saw blade penetrationmeasurement system and designated parts thereof. The terminologyincludes the words above specifically mentioned, derivatives thereof andwords of similar import.

Additionally, as used in the claims and in the corresponding portion ofthe specification, the word “a” means “at least one”. Further, unlessotherwise defined the word “about” when used in conjunction with anumerical value means a range of values corresponding to the numericalvalue plus or minus ten percent of the numerical value. Still further,the word “or” has the meaning of a Boolean inclusive “Or”. For example,the phrase “A or B” means “A” alone or “B” alone or both “A” and “B”.

Referring to the drawings in detail, where like numerals indicate likeelements throughout there is shown a first embodiment of the saw bladepenetration measurement system generally designated 100, and hereinafterreferred to as the “measurement system” 100, in accordance with thepresent invention. The measurement system 100 is for determining, withrespect to a reference point (not shown), a depth of penetration of thecutting edge 16 a of a saw blade 16 in a cut. The saw blade 16 may beoscillated by a drive 24 in a saw housing 26 of any typical well knownsurgical saw. In this regard and as may be appreciated below, ameasurement system 100 may be provided with an existing surgical saw(e.g., as a retrofit). In further embodiments described in greaterdetail below, a measurement system 400 may be provided that is at leastpartially integrated into a saw 50 (e.g., as shown in FIGS. 8A-8C)and/or saw 700 shown in FIGS. 18-21C.

Referring to FIGS. 2, 5A, 5B and 5C, the measurement system 100 mayinclude a saw blade displacement measurement assembly 102, a saw bladeload measurement assembly 104, and a controller assembly 106. Thedisplacement measurement assembly 102 is connected to the saw housing26. The connection can be made by a variety of well known mountingmethods such as a mount that clamps to the displacement measurementassembly 102 and is attached to the saw housing 26 by one or morethreaded fasteners. Alternative methods such as welding or adhesivebonding could also be used. The displacement measurement assembly 102may include a first sensor 108 that outputs a first signal 108 srepresentative of a displacement, with respect to the reference point,of the cutting edge 16 a of the saw blade 16 in the cut being sawed. Thedisplacement measurement assembly 102 preferably has an extension 110that is displaceable along a direction of sawing. The extension 110 hasa distal end 110 a that can be placed in registry with the referencepoint when the cutting edge 16 a of the saw blade 16 is positioned atthe outer surface of the medium to be cut and maintained in registrywith the reference point throughout the sawing process. The referencepoint may be any anatomical structure proximal to the desired locationof the cut to be sawed. Additionally or alternatively, the referencepoint may be established using a bushing disposed relative to the sawblade or with respect to a cutting guide as will be described in greaterdetail below. The extension 110 has a proximal end 110 b that isattached to the first sensor 102. In one embodiment, the sensor 102 maybe a linear variable differential displacement transducer (“LVDT”),although other appropriate displacement sensors may also be used asdescribed in greater detail below.

A second sensor 118 may be located within the housing 26 outputs asecond signal representative of a force applied to the cutting edge 16 aof the saw blade 16. In one embodiment, the second sensor 118 may be ahydraulic pressure transducer and a portion within the housing 26 and/orthe drive 24 may form a hydraulic chamber connecting the second sensor118. In another embodiment, the second sensor 118 may include a loadcell, such as a piezo-electric device, located within the housing 26and/or the drive 24. An electrical conductor electrically connects thepiezo-electric device to the controller assembly 106. In this regard, itmay be appreciated that depending upon the drill configuration, thesecond sensor 118 may be arranged in various manners relative to the sawblade 16. For instance, in a sagittal saw or an ultrasonic saw, an axialforce (i.e., extending between the cutting edge and the attachment ofthe saw blade to the saw) may be applied relative to the distal cuttingedge of the saw blade such that the second sensor 118 may measure theaxial force to determine the force acting on the cutting edge. In areciprocating saw, the load may be transverse (i.e., orthogonal to theattachment of the saw blade to the saw). Thus, the second sensor 118 maybe configured to measure the load acting on the cutting edge, which maybe orthogonal to an axis defined along the attachment of the saw bladeto the saw.

The controller assembly 106 is in electrical communication with thefirst sensor 108 and/or the second sensor 118. In an embodiment, thecontroller assembly 106 has a controller housing 146 integral with thesaw housing 26. However, with further reference to FIG. 13A, thecontroller housing 146 may also be provided as a remote unit. Thecontroller assembly 106 includes a processor 148 in electricalcommunication with the first and second sensors 108, 118 and with a modeselector 150 having a mode selector switch 154 and a display 152 havinga reset button 153. The display 152, the reset button 154 and the modeselector switch 154 may be mounted in a panel 156 of the controllerhousing 146. Alternatively, the display 152 or the reset button 153 orthe mode selector 154 or any combination thereof could be separatelyhoused in the remote control unit that communicates with the first andsecond sensors 108, 118 by a wired or wireless link. Furthermore, thereset button 153 may be provided as a separate hardware portion such asa foot pedal or the like. In this regard, the hardware portioncomprising the reset button 153 be in wired or wireless communicationwith the controller assembly 106. In this regard, the foot pedal may beused to set or reset the reference point of the controller and/or toindicate a new sawing operation. The display 152 is for indicating themeasured displacement of the cutting edge 16 a of the saw blade 16 tothe user. The display 152 is controlled by the processor 148. Thedisplay 152 may continuously indicate the changing displacement of thecutting edge 16 a of the saw blade 16 during the sawing of a cut and mayalso indicate the depth of the cut at the when the saw blade 16 passesfrom one medium to another (i.e., when the saw has passed completelythrough a bone).

For instance, with continued reference to FIGS. 13A and 13B, the display152 may be a touch sensitive display (e.g., a resistive or capacitivetype touch screen display). The display 152 may include an indication ofa cut length 160, the saw speed 162, etc. The display 152 may alsoinclude patient information 168. The controller unit 106 may include aport 170 for engagement of a wired plug connection 172 with the saw 50.In this regard, the saw 50 may be connected to the controller assembly106 to supply power to the saw 50 and communicate data between the saw50 and the controller assembly 106

Referring to FIGS. 1, 3, 4, 5, the processor 148 may be configured tooperate in a first mode for cut length measurement for a cut thatextends through the entirety of the medium to be cut. Thus, withreference to FIG. 5, the processor 148 may be configured to output athird signal 148 s representative of the depth of penetration of thecutting edge 16 a of the saw blade 16 when the cutting edge 16 a of thesaw blade 16 passes from a first medium having a first density (i.e.,bone 12) to the second medium having a second density (i.e., asurrounding medium 14 such as air or soft tissue). The third signal 148s may be based on the first and second signals 108 s, 118 s. Preferably,the third signal 148 s is output at a second time derivative of thefirst signal 108 s being greater than zero and a first time derivativeof the second signal 118 s being less than zero. In other words apositive acceleration of the saw blade 16 and a concurrent reduction inthe force applies to the cutting edge 16 a of the saw blade 16 triggerthe third signal 148 s. However, the third signal 148 s may also bebased on other mathematical transforms of the first or second signals108 s, 118 s or raw values of the first signal 108 s or 118 s. Forinstance, the third signal 148 s may be based on the first and/or secondderivative of the first signal 108 s (e.g., the displacement signal).For instance, the third signal 148 s may be generated upon a concurrentpositive state of the first signal 108 s, a first derivative of thefirst signal 108 s with respect to time (e.g., a velocity signal), and asecond derivative of the first signal 108 s with respect to time (e.g.,an acceleration signal). In this regard, any one or more of thedisplacement signal, the velocity signal, and acceleration signal may beactually measured to derive the displacement signal, a velocity signal,and acceleration signal. Thus, the third signal 148 s may be dirtderived using a single sensor, such that the force sensor describedabove in an embodiment of the saw may not be employed in allembodiments.

The processor 148 is also configured to operate in a second mode for sawblade penetration measurement (e.g., using the mode selector 150 andmode selector switch 154). The second mode of operation is directed tothe case where a predetermined depth is established. As such, theprocessor 148 may monitor the first signal 108 s to determine when thepredetermined depth is reached. Once reached, the third signal 148 s maybe output. In this regard, the value of the first signal 108 s alone maybe used in the second mode of operation to cease the sawing when thepredetermined depth is reached. As may be appreciated, rather than thesecond time derivative of the first signal 108 s that indicates anacceleration of the blade, the value of the signal 108 s alone may beutilized. That is, a “saw-to-depth” mode may be established where thesaw operate until a predetermined depth to reach is determined by thefirst signal 108 s, and thereupon the operation of the saw is terminatedonce the predetermined depth is reached.

Additionally or alternatively, the third signal 148 s may be at leastpartially based on additional parameters other than the first signal 108s and second signal 118 s. For instance, in at least some embodiments,the third signal 148 s may be at least partially based on a parameterassociated with the oscillation of the saw blade 16. For instance, thespeed of the drive 24 oscillating the saw blade 16, the resistanceagainst the saw blade (e.g., is measured by the load on a motor drivingoscillation of the saw blade), or another appropriate parameterregarding the oscillation of the blade 16 may be utilized in outputtingthe third signal 148 s. Further still, parameters such as the length ofthe cutting edge of the saw blade 16, the bone to be sawed, or otherappropriate parameters may be utilized in determining the third signal148 s.

Furthermore, the generation of the third signal 148 s may at leastpartially be customized based on the patient. In this regard,information regarding the patient may be provided to the controllerassembly 106 and utilized by the processor 148 in determining the thirdsignal 148 s. For instance, a patient's age, sex, and/or otherdemographic information may be provided. As may be appreciated, thedemographic data of the patient may provide a correlation to expectedbone density or other parameter regarding an expected property of thepatient's anatomy based on the demographic data of the patient. In thisregard, the demographic data may be used to correlate an expectedparameter associated with the patient's anatomy (e.g., bone density)that may be used as a factor in generation of the third signal 148 s. Inaddition, direct measurement of an anatomical parameter (e.g., bonedensity) for a given patient may be provided directly to the controllerassembly 106, thereby potentially eliminating the need to estimate theparameter based on demographic data.

Referring to FIG. 6, there is shown a block diagram of a first methodfor determining, with respect to a reference point, the depth ofpenetration of the cutting edge 16 a of a oscillating saw blade 16 in acut when the cutting edge 16 a of the saw blade 16 transitions from afirst medium having a first density, such as the hard outer cortex 12 ofa cortical bone 10, to a second adjacent medium 14 having a seconddensity, such air or tissue surrounding the outer surface of thecortical bone 10. (FIG. 1B).

An initial position of the cutting edge 16 a of the saw blade 16relative to the reference point is established (Step 205). The initialposition may be established by placing the cutting edge 16 a of the sawblade 16 against the outer surface of the cortical bone to be sawed andby extending the distal end 10 a of the extension 110 of thedisplacement measurement assembly 102 to the reference point, such as ananatomical structure proximal to the desired location of the cut to becreated. As will be appreciated in the discussion of the embodimentsbelow, the reference point may also be established by a bushing memberof a saw blade assembly that is engaged with a displacement sensing armof a displacement sensor. For instance, the bushing member may have areference surface contactable with the bone to be sawed. Further still,the reference point may be established relative to a cutting guide orthe like.

In any regard, with the cutting edge 16 a of the saw blade 16 and themeasurement system reference point in the above positions (i.e., alignedat a surface of the medium to be sawed), the measured displacement ofthe saw blade 16 is set to zero by pressing the reset button 153. Uponcommencement of sawing, a first signal representing the depth ofpenetration of the cutting edge 16 a of the saw blade 16 in the cut isoutput (Step 210). A second signal representing a force applied to thecutting edge of the saw blade is output (Step 215). A third signal basedon the first and second signals and representative of when the cuttingedge of the saw blade passes from the first medium to the second mediumis output (Step 225). Preferably, the third signal is output when thesecond time derivative of the first signal is greater than zero and afirst time derivative of the second signal is less than zero.Additionally or alternatively and as described above, the third signalmay be based only on the first signals and/or mathematical transformsthereof.

The third signal may cause an output device to generate an alert thatmay be perceivable by a user of the saw. As such, upon determinationthat the saw has passed through the bone (e.g., as described above), thealert may provide feedback to the user that the bone has been sawedthrough. As such, the alert may be an auditory alert such as a tone orthe like. In another embodiment, the third signal may cause a change inthe speed of the motor of the saw. For instance, the saw may be slowedsuch that the user may be alerted to the fact that the saw has passedthrough the bone. Further still, the saw may be automatically stopped atthe occurrence of the third signal. It may be appreciated that any otheruser perceivable alert may be provided including, for example, a visual,tactic, or other type of user perceivable feedback.

Referring to FIG. 7, there is shown a block diagram of a second methodfor determining, with respect to a reference point, the length of a cut.The predetermined depth to be reached by the saw blade is provided (Step305). An initial position of the cutting edge 16 a of the saw blade 16relative to the reference point is established (Step 310), preferably ina manner similar to Step 205 discussed above. The displacement of thecutting edge 16 a of the saw blade 16 is continuously determined (Step315). The processor 148 may determine if the displacement of the cuttingedge 16 a of the saw blade is equal to the predetermined depth providedin Step 305. If the depth does not equal the predetermined depth (i.e.,is less than the predetermined depth), the cutting procedure maycontinue. Once the displacement equals the predetermined depth, the sawmay be stopped (Step 325).

The components used to construct the present invention may include avariety of materials that are customarily used in the manufacture ofsurgical saws. One having ordinary skill in the art will readilyappreciates the materials that most desirably may be used to constructthe present invention. In one embodiment, however, the sawing mechanism,saw blade displacement measurement assembly, the saw blade loadmeasurement assembly and the structural elements of the controllerassembly may be constructed of a combination of polymeric materials(e.g., high strength plastic), polymers and stainless steel.

One embodiment of a saw with an improved displacement sensor including adisplacement sensing arm that extends from the saw may be provided. Forexample, such a displacement sensing arm may be provided that maycoordinate with a bushing member of a saw blade assembly that may beused with the saw. However, other embodiments are described below wherethe displacement sensing arm may coordinate (e.g., contact or be engagedwith) a cutting guide to establish a reference point. However, in thecase of a bushing, the bushing may move along the saw blade in adirection corresponding to the direction of cutting. Upon engagement ofthe bushing and the displacement sensing arm, the bushing anddisplacement sensing arm may undergo corresponding movement. As such,the bushing may be disposed in contact with the medium to be sawed whenthe cutting edge of the saw blade is in contact with the medium. Assuch, a reference point may be established when the bushing and cuttingedge of the saw blade are both in contact with the medium to be sawed.As the bushing is located adjacent to (e.g., partially or fullysurrounding the saw blade or operatively engaged with the saw blade),the bushing may facilitate contact with the medium at or very near thelocation to be sawed prior to creating a cut as described above. In thisregard, the reference point may be more accurately maintained as thebushing may contact at least a portion of a periphery of the cut createdin the medium sawed. That is, the bushing may remain in intimate contactwith the medium to be sawed adjacent to the cut created. This mayprevent false displacement readings attributable to the foregoingproblems associated with an offset extension 110. Furthermore, theamount of contact of the saw may be localized at the location to besawed, thus allowing for potentially less intrusion when performingsawing operations.

For example, with additional reference to FIGS. 8A-8C and 9, anembodiment of a saw 50 with a measurement system 400 is shown. The saw50 may integrally include at least some components of the measurementsystem 400 to facilitate operation of the measurement system 400 inconnection with the saw 50 (e.g., which may be according to thedescription above regarding measurement system 100). For example, atleast a portion of a displacement sensor 410 may be integrated into ahousing 26 of the saw 50. In this regard, the displacement sensor 410may include a depth sensing arm 412 that is specifically adapted forengagement with a bushing 452 of a saw blade assembly 60 that may beengaged by the chuck 420 of the saw 50.

In this regard, the depth sensing arm 412 may be used to establish areference point from which displacement of the saw blade 16 may bemeasured as described above. In this regard, as follows herein, ageneral description of the features and operation of the saw 50 used inconjunction with the saw blade assembly 60 is provided.

As may be appreciated in FIGS. 8A-8C, the displacement sensor 410 mayinclude a depth sensing arm 412 that may extend from the saw housing 26.For example, the depth sensing arm 412 may extend distally (e.g., from adistal face 30 of the saw housing 26) in a direction corresponding withthe direction in which the saw blade 16 extends from a chuck 420 of thesaw 50. At least a portion of the displacement sensing arm 412 mayextend from the saw housing 26 parallel to a cutting direction 120 ofthe saw 50. The depth sensing arm 412 may also include a distal portion414 that is adapted to engage a bushing 452 provided with the saw bladeassembly 60. As used herein, distal may correspond to a direction fromthe saw 50 toward the cutting edge 16 a of the saw blade 16 and proximalmay correspond to a direction from the cutting edge 16 a of the sawblade 16 toward the saw 50. In this regard, at least a portion of thedepth sensing arm 412 (e.g., the distal portion 414) may be adapted toengage the bushing 452 of the saw blade assembly 60 as will be describedin more detail below. In any regard, at least a portion of the depthsensing arm 412 may extend into the housing 26. With further referenceto FIG. 9, the housing 26 may contain a coil 416. As such, a proximalend 418 of the displacement sensing arm 412 may interface with the coil416 of the displacement sensor 410 that may be disposed within the sawhousing 26.

Specifically, in FIG. 9, the depth sensing arm 412 is shown in aretracted position relative to the saw blade 16. As such, this retractedposition shown in FIG. 9 may occur when the saw blade 16 is advancedrelative to the bushing 452 during sawing (e.g., such that the portionof the saw blade extending beyond the distal edge of the bushing 452would be disposed in the medium to be sawed). In this regard, theproximal end 418 of the displacement sensing arm 412 is disposed withinthe coil 416 of the displacement sensor 410. Accordingly, thedisplacement sensor 410 may comprise an LVDT sensor as described abovethat is adapted to sense the position of a core 422 relative to a coil416. The displacement sensing arm 412 may incorporate a core 422 at theproximal end 418 thereof. Accordingly, as the proximal end 418 of thedisplacement sensing arm 412 is moved relative to the coil 416, thelocation of the core 422 may be determined to provide an outputcorresponding to the position of the core 422, and in turn thedisplacement sensing arm 412 relative to the saw housing 26. That is,the depth sensing arm 412 may be displaceable relative to the coil 416such that the displacement sensor 410 may be operable to sense a changein position of the depth sensing arm 412 relative to the saw housing 26and output a measure of the displacement that may be used as describedabove in determining a depth of a cut. In an embodiment, the totalmeasurable travel of the core 422 relative to the coil 416 may be atleast about 2.5 in (6.4 cm). Furthermore, the resolution of the outputof the displacement sensor 410 may be about 0.1% (e.g., about 0.002inches (0.06 mm) for a sensor having a total measurable travel of 2.5inches).

While a LVDT displacement sensor is shown and described in relation tothe saw 50 shown in the accompanying figures, it may be appreciated thatother types of displacement sensors may be provided. For instance, thesensor may provide for the absolute or relative measurement of theposition of the distal end 418 of the displacement sensing arm 412 toprovide a displacement measure. For instance, in another embodiment, anoptical displacement sensor may be provided. Other types of displacementsensors are also contemplated such as, for example, a capacitivedisplacement sensor, ultrasonic sensors, Hall effect sensors, or anyother sensors known in the art capable of outputting an absolute orrelative position measure.

In an embodiment, the coil 416 may define a passage 424 extending atleast partially through the housing 26. Specifically, the passage 424may extend from a proximal face 32 of the housing 26 to the distal face30 of the housing 26. That is, the passage 424 may extend entirelythough the housing 26. An end cap 34 may be provided that is operable toclose the proximal end of the passage 424 at the proximal face 32 of thesaw housing 26. Furthermore, a biasing member 426 (e.g., a coil spring)may be provided in the passageway 424 at a proximal end thereof. Thebiasing member 426 may be provided between the end cap 34 and theproximal end 418 of the displacement sensing arm 412. In this regard,the biasing member 426 may act on the proximal end 418 of thedisplacement sensing arm 412 to bias the displacement sensing arm 412distally relative to the passage 424 and saw housing 26.

As such, the displacement sensing arm 412 may include features thatselectively prevent ejection of the displacement sensing arm 412 fromthe distal end of the passage 424. For example, the displacement sensingarm 412 may include at least one flat 428 that extends along a portionof the arm 412. At the proximal and distal extents of the flat 428, thedisplacement sensing arm 412 may include shoulders 436 that project fromthe flats 428 (best seen at the distal portion 414 in FIG. 8B and at theproximal portion 418 in FIG. 9). As such, at the proximal opening of thepassage 424, a selectively displaceable stop 438 may be disposedrelative to the flat 428 such that the flat 428 may move relative to thestop 438, but interfere with the shoulder 436 defined in thedisplacement sensing arm 412 to prevent passage of the shoulder 436beyond the stop 438. In this regard, the length of the displacementsensing arm 412 along which the flat 428 extends may be moveablerelative to the stop 438, and the stop 438 may limit proximal and distalmovement of the displacement sensing arm 412 beyond the stop 438.

However, the stop 438 may be displaceable upon depressing, for example,a button 440 provided on an exterior of the housing 26. Thus, upondepressing the button 440, the stop 438 may be displaced away from thedisplacement sensing arm 412 to allow the shoulder 436 to pass distallyfrom the distal end of the passage 424 such that the displacementsensing arm 412 may be removed entirely from the passage 424. The distalend of the flats 438 may include a detent 442 that may be engageablewith the stop 438 so as to maintain the displacement sensing arm 412 ina proximally disposed, retracted position relative to the housing (e.g.,as shown in FIG. 9). Once the button 440 is depressed and released, thedetent 442 at the proximal end of the flat 428 of the displacementsensing arm 412 may be released by the stop 438 and the displacementsensing arm 412 may move proximally (e.g., under influence of thebiasing member 426). The displacement sensing arm 412 may moveproximally until the shoulder 436 at the distal end of the flat 428 areengaged to prevent further distal movement of the displacement sensingarm 412. Accordingly, the displacement sensing arm 412 may be retainedin a retracted position (e.g., for improved visibility of the distal endof the saw blade 16), released to be moveable relative to and biasedproximally with respect to the housing 26, and removable altogether fromthe housing 26.

In the latter regard, removal of the displacement sensing arm 412 andbiasing member 426 from the passage 424 may allow for separate cleaning(e.g., in an autoclave) of those members. Additionally, removal of theend cap 34 may allow for a cleaning apparatus (e.g., a brush or thelike) to be passed through the full length of the passage 424 tofacilitate cleaning thereof.

As referenced above, the distal portion 414 of the displacement sensingarm 412 may be adapted to engage a saw blade assembly 60 (e.g., abushing 452 thereof) that is correspondingly adapted for use with thesaw 50. For instance, as shown in FIGS. 8A-8B and FIG. 9, thedisplacement sensing arm 412 may generally be linear along the proximalportion 418 of the displacement sensing arm 412. In this regard, theproximal portion 418 may be adapted to be collinear with the passage 424and moveable within the passage 424.

Furthermore, the distal portion 414 of the displacement sensing arm 412(e.g., the portion distal to the linear portion of the displacementsensing arm 412) may extend from the linear portion of the displacementsensing arm 412 toward the saw blade assembly 60 that may be engaged bythe chuck 420 of the saw 50. In this regard, the linear portion of thedisplacement sensing arm 412 may be substantially parallel to and offsetfrom the cutting direction 120. The distal portion 414 may extend fromthe linear portion in a direction corresponding with the offset suchthat the distal portion 414 extends toward the saw blade assembly 60.This may facilitate engagement between the displacement sensing arm 412and the bushing 454 of the saw blade assembly 60. As shown, in FIGS.8A-8B and 9, the distal portion 414 may be an at least partially arcuatemember extending along a radius of curvature toward the saw bladeassembly 60. However, the distal portion 414 may be shaped differently(e.g., the distal portion 414 may be a linear portion extending at anangle or perpendicularly from the proximal 418 toward the saw bladeassembly 60).

The saw blade assembly 60 may include a shank that is disposed adjacentto a proximal end of the assembly 60. Furthermore, the assembly 60 mayinclude a cutting edge at the distal end thereof. The cutting edge mayinclude a cutting edge that, when oscillated serves to cut the mediuminto which the blade 16 is advanced as per a standard saw blade. Thedirection in which the saw blade is advanced during a cutting operationmay be referred to as a cutting direction 120 that is generallyorthogonal to the cutting edge. A blade member may extend between theshank and the cutting edge. The cutting edge, body, and shank maycollectively define the saw blade 16.

In addition to the saw blade 16, the saw blade assembly 60 may alsoinclude a bushing 452 as referenced above. The bushing 452 may engagethe blade member to facilitate relative movement of the bushing 452relative to the blade member along a direction corresponding to thecutting direction 120. For example, the bushing 452 may include anaperture through which at least a portion of the blade member may bedisposed. The aperture may form an opening that extends at least in adirection corresponding to the cutting direction 120 of the saw blade16. The opening may be sized to receive the blade member therein suchrelative movement between the opening and the blade member is provided.As such, the saw blade 16 may be free to oscillate within the aperture,and the bushing 452 may slideably engage the member for relativemovement therebetween that is constrained along the directioncorresponding to the cutting direction 120.

The bushing 452 may include an engagement member that is disposed on thebushing 452 and adapted for engagement with a displacement sensing arm412 of a saw 50 to which the saw blade assembly 60 is engaged. Forinstance, the engagement member may include a post 456 extending fromthe bushing 452 (FIG. 10). The post may extend away from the cuttingdirection 120 of the saw blade assembly 60. In an embodiment, the postmay extend perpendicularly to the cutting direction 120. Accordingly,the post may engage a hole provided on the distal portion of thedisplacement sensing arm 412. In this regard, the post may extend intothe hole. Movement of the bushing 452 relative to the saw blade 16 in adirection corresponding to the cutting direction 120 may result in thepost acting on the hole such that the displacement sensing arm 412undergoes corresponding movement upon movement of the bushing 452relative to the saw blade 16. In turn, as described above, the core atthe proximal portion the displacement sensing arm 412 may also undergocorresponding movement relative to the coil 416, which may be detectedby the displacement sensor 410 and output as a displacement measure.

It may be appreciated that other arrangements for engaging the bushing452 with the displacement sensing arm 412 may be provided so that thebushing 452 and displacement sending arm 412 undergo correspondingmovement. For example, other structures such as clasps, fasteners, orother mechanisms may be utilized to engage the bushing 452 to thedisplacement sensing arm 412. Furthermore, the bushing 452 may, in someembodiments, be integrally defined on the distal portion 414 of thedisplacement sensing arm 412. In this regard, a standard saw blade 16may be engaged with a chuck 420 of the saw 50 and the bushing 452 may bedisposed relative to the blade 16. In any regard, the bushing 452 may bepivotal relative to the displacement sensing arm 412 (e.g., in adirection perpendicular to the cutting direction 120) to facilitate easeof engagement of the bushing 452 with the displacement sensing arm 412or the bushing 452 with the saw blade 16 when engaging the saw blade 16with the chuck 420 of the saw 50.

For instance, with further reference to FIG. 14, a schematic sectionview of a saw blade 16 that has been advanced into a medium 550 isshown. The bushing 452 may be disposed about the saw blade 16. As such,the bushing 452 may be disposed about the periphery of the cut 556created upon advancement of the saw blade 16 into the medium 550. Thatis, the bushing 452 may remain in contact with the surface 552 of themedium 550 upon advancement of the saw blade 16 into the medium 550. Inthis regard, the bushing 454 may include a reference surface 554 at adistal portion thereof. The reference surface 554 may contact thesurface 552 of the medium 550 to be sawed. As such, prior to initiationof the sawing when the cutting edge 16 a of the saw blade 16 is also incontact with the surface 552, the displacement sensor 410 may be set toestablish the reference point. Accordingly, as the saw blade 16 isadvanced, the reference surface 554 may remain in contact with thesurface 552 of the medium 550. The reference surface 554 may contact thesurface 552 about a periphery of the cut 556. In an embodiment, thereference surface 554 may extend about a majority or substantially allof the saw blade 16 such that the reference surface 554 may also extendabout a majority of or substantially all of the periphery of the cut556. The distally biased displacement sensing arm 412 may act on thebushing 452 (e.g., by way of post 462 received in hole 464) to maintainthe bushing 452 in contact with the surface 552. In any regard, thedisplacement (d) of the cutting edge 16 a of the saw blade 16 relativeto the reference surface 554 of the bushing 454 may be measured uponcorresponding movement of the core 422 at the proximal end 418 of thedisplacement sensing arm 412 relative to the coil 416.

In this regard, measurement of the displacement of the cutting edge 16 aof the saw blade 16 relative to the reference surface 554 of the bushing454 that is maintained against the surface 552 of the medium 550 to besawed may provide improved accuracy regarding the displacement of thecutting edge 16 a into the cut 556. As described above, as the referencesurface 554 is maintained in contact with the medium 550 adjacent to theperiphery of the cut 556, there is less possibility for relativemovement between the bushing 452 and the medium 550 that may introduceerror into the measured displacement d. Furthermore, as the bushing 452is in contact with the medium 550 adjacent to the cut 556, the contactwith the patient required to obtain the measurement is lessened as theextension 110 may not need to contact the patient in a location awayfrom the cut 556. Thus, the sawing operation is less invasive, thusimproving patient outcomes.

A number of additional features may also be provided for the saw 50and/or saw blade assembly 60 that are described in conjunction with theembodiment of the saw 50. It may be appreciated that these features maybe provided with other types of saws and/or saw blade assemblies 60 andare not required to be used in conjunction with a saw 50 and saw bladeassembly 60 incorporating features for coordinated operation between thedisplacement sensor 410 and saw blade assembly 60 as described above.

For instance, as may be further appreciated with reference to FIGS. 11and 12, a saw blade 16 may incorporate features that prevent reuse ofthe saw blade 16. In this regard, surgical saw blades are often employedas single use items such that the blades are specifically designed to beused for a single procedure or portion thereof and disposed after userather than being reused. There are several rationales for doing so,including the safety of the patient to ensure that the saw blade 16 tobe used in a procedure has not been worn or damaged by use in previousprocedures. In this regard, the features described below may helpprevent the saw blade 16 from being reused. As may be appreciated, thesaw blade 16 disclosed in this respect may be used in a saw bladeassembly 60 as described above.

Specifically, the saw blade 16 may include a destructible portion 466 ofthe shank. The destructible portion 466 may be degraded or destroyedwhen exposed to common cleaning procedures to which surgical instrumentsare routinely exposed. Upon destruction of the destructible portion 466,the shape of the shank may be altered. The altered shape of the shankmay result in a reduced ability to engage the saw blade 16 with a chuck420. Such cleaning procedures may include exposure to steam cleaning atelevated heat and/or pressure in an autoclave process or may includeexposure to cleaning chemicals or the like. In this regard, when, forexample, the destructible portion 466 is exposed to temperaturesassociated with cleaning in an autoclave, the destructible portion 466may be degraded or destroyed (e.g., by melting or other degradation dueto heat) to prevent reuse of the saw blade assembly 60. Accordingly, inan embodiment, the melting temperature of the destructible portion maybe greater than an operating temperature (e.g., substantially similar toroom temperature or 22.3° C.+/−20° C.). Accordingly, in an embodiment,the melting temperature may be not less than about 50° C. and notgreater than about 130° C. In an embodiment, the melting temperature ofthe destructible portion may be not less than about 60° C. and notgreater than about 110° C.

While autoclave cleaning is a common method of sterilization andcleaning of instruments between procedures, it may be appreciated thatother methods of cleaning may be employed. As such, the destructibleportion 466 may be adapted to be degraded or destroyed during suchcleaning procedures. For example, the destructible portion 466 couldalternatively or additional be adapted to be degraded or destroyed uponexposure to a cleaning element such as a cleaning chemical or the like.In any regard, upon an attempt to sterilize or otherwise clean the sawblade assembly 60 for reuse, the destructible portion 466 may bedestroyed or degraded to the point of eliminating the effectiveness ofthe saw blade assembly 60 to prevent reuse of the saw blade assembly 60.

With further reference to FIG. 11, one particular embodiment of a sawblade assembly 60 including a destructible portion 466 is shown wherethe destructible portion may include a portion of the shank of the sawblade assembly 60. As shown, the destructible portion 466 includes aproximal end of the shank. As such, at least a portion of a sidewalland/or an endwall of the shank may be defined by the destructibleportion 466. As may be appreciated, the shank sidewall and endwall maybe adapted for engagement with the chuck such that the chuck contactsthe sidewalls and endwall (or tabs) upon engagement with the shank.

For instance, the chuck may include a correspondingly-shaped openingthat is sized to have corresponding sidewalls that may contact the tabswhen the shank is received in the chuck. As such, upon receipt of theshank in the chuck, the chuck may define a bearing surface interfacethat allows the chuck to impart an oscillating motion to the saw blade16.

Accordingly, when, as shown in FIG. 12, the destructible portion 466 isdestroyed or degraded and may be removed. The result may be at least alack of registration of the shank relative to the chuck. This mayprohibit the ability of the saw blade assembly 60 to be used because thelack of registration may prevent the saw blade 16 from properly turningso as to at least inhibit the use of the saw blade assembly 60 in aprocedure. Additionally or alternatively, the destructible portion 466may be degraded to the point where the shank is no longer receivable bythe chuck (or other attachment device).

As may also be appreciated in FIGS. 11 and 12, the shank may includechuck engagement features that may be engaged by the chuck to retain thesaw blade assembly 60 relative to the chuck. For instance, the chuck mayinclude retention pins that are biased to extend into the chuck openingin an engaged position to engage detents of the shank.

Furthermore, the saw 50 may include a removable chuck 420 that providesfor quick interchange and/or removal of the chuck. As may further beappreciated from FIG. 9, the saw 50 may include a drive having a motor432 and gearbox 434. The drive 430 may engage a chuck 420. Specifically,the chuck 420 may be provided in removable engagement with the drive 430such that the chuck 420 may be releasably engaged with the drive 420.The chuck 454 may include a chuck drive coupling at a proximal endthereof. In this regard, the saw 50 may include a corresponding sawdrive coupling that engages with the chuck drive coupling to impartoscillating motion from the drive 430 to the chuck 420. In this regard,the chuck 420 may be detachable from the saw 50.

As may be appreciated, when sawing using the saw 50, a second sensor formeasurement of force acting on the cutting edge 16 a of the saw blade 16may also be provided. In this regard, a second sensor 118′ (e.g., aforce sensor such as piezoelectric crystal) may be disposed proximallyto the saw drive 430. In turn, force acting on the cutting edge 16 a ofthe saw blade 16 as it is advanced in the sawing process may betransferred to the second sensor 118′ via the saw drive 430. That is,the force acting on the cutting edge 16 a of the saw blade 16 may betransferred through the shank of the blade 16 to the chuck 420, and thesaw drive 420. In turn, the drive 430 may act upon the second sensor118′ to produce an output corresponding to the force acting on thecutting edge 16 a. In this regard, it may be appreciated that the rigidassembly of the saw drive 430, chuck 420, and saw blade 16 may transmitthe force acting on the cutting edge 16 a of the saw blade 16 to thesecond sensor 118. It may further be appreciated that the saw drive 430may be fixed relative to the saw housing 26 so as to impart oscillationto the chuck 420. At least a majority of the force acting on the cuttingedge 16 a of the saw blade 16 may be transferred to the second sensor118. In an embodiment, the second sensor 118 may have a range ofmeasurable force from about 0 lbf (0 N) to about 100 lbf (445 N). In anembodiment, the second sensor 118 may have a range of measurable forcefrom about 0 lbf (0 N) to about 25 lbf (111 N). The second sensor 118may have a precision of at least about 1% of the maximum measurableforce. Accordingly, in an embodiment, the second sensor may have aprecision of at least about 0.25 lbf (1.1 N). In an embodiment, thesecond sensor 118 may have a precision of 0.5% (e.g., about 0.125 lbf(0.56 N) in an embodiment).

In this regard, the saw drive 430, as shown best in FIG. 9, may bemounted to the saw housing 26 by way of a suspension member 494. Thesuspension member 494 may be operatively engaged to the saw housing 26and the saw drive 430 so as to maintain the saw drive 430 stationary totransfer force acting on the cutting edge 16 a of the saw blade 16 tothe second sensor 118. As such, the suspension member 494 may besupportively engaged to the saw drive 430 at a first end of thesuspension member 494. The suspension member 494 may also be affixed tothe saw housing 26. The suspension member 494 may allow for linearmovement along the cutting direction 120. In this regard, the suspensionmember 494 may comprise a spring member that allows for motion relativeto the direction along the cutting direction 120. The spring member mayhave a spring coefficient slight enough relative to the directioncorresponding to the cutting direction 120 such that the force resultingfrom displacement of the suspension member 494 may be insignificant(e.g., less than about 1%, less than about 0.5% or even less than about0.1%) of the force applied to the cutting edge 16 a of the saw blade 16during the sawing operation.

As shown in FIGS. 15A-C, an embodiment of a saw 50A with two measurementsystems is shown. Displacement sensors similar to the displacementsensor 410 of FIG. 9 may be integrated into a housing of the saw 50A. Inthis regard, the displacement sensors may each include a depth sensingarm 412A, B that is specifically adapted for engagement with a bushing452A, B. In this regard, the depth sensing arms 412A, B may be used toestablish reference points from which displacement of the saw blade 16may be measured as described above.

The displacement sensors may include a depth sensing arm 412A, B thatmay extend from the saw housing. For example, the depth sensing arm412A, B may extend distally (e.g., from a distal face 30 of the sawhousing) in a direction corresponding with the direction in which thesaw blade 16 extends from a chuck of the saw 50A. At least a portion ofthe displacement sensing arms 412A, B may extend from the saw housingalong the length of the saw blade 16 of the saw 50A. The depth sensingarms 412A, B may also include a distal portion 414 that is adapted toengage a bushing 452A, B. As used herein, distal may correspond to adirection from the saw 50A toward the cutting edge of the saw blade 16and proximal may correspond to a direction from the cutting edge of thesaw blade 16 toward the saw 50A. In this regard, at least a portion ofthe depth sensing arms 412A, B (e.g., the distal portion 414) may beadapted to engage the bushings 452A, B of the saw blade assembly. In anyregard, at least a portion of the depth sensing arms 412A, B may extendinto the housing. The housing of the saw 50A may contain components forboth of the sensing arms 412A, B that are shown within the housing 26 ofFIG. 9. As such, a proximal end of the displacement sensing arm 412Balso interfaces with a coil of a displacement sensor that may bedisposed within the saw housing.

FIG. 15C shows when the cut has been completed and one side of themedium 550 has been dislodged. This causes one of the bushings 452B torelease due to a lack of counter force from the medium 550. When thisoccurs the processor will receive a signal from the position sensorassociated with the second bushing 452B that is quite different from asignal from the position sensor associated with the first bushing 452A.In one embodiment, the processor will generate a signal indicating thatthe cut is complete when the signals from the two position sensorsdiffer by greater than a previously defined threshold amount. Thisgenerated signal causes an automatic slowing of motion or stoppingaltogether of the saw motor. An output device may generate an alert(visual, tactile or audible) for a saw user based on the generated cutcompletion signal.

FIG. 16 shows the saw 50 used with an exemplary cutting guide/jig 480.In one embodiment, the cutting guide/jig 480 is U-shaped for receiving aportion of a patient's anatomy. The cutting guide/jig 480 includes twoopposing walls. The walls include slot guides 482 that receive the sawblade 16. The slot guides 482 can be thin enough to act as bearingmembers to the received saw blade 16 without cause undue friction duringoscillation of the saw blade. As the saw blade 16 is received within theslot guides 482 a displacement sensing arm 412 uses the side of thecutting guide/jig 480 as a reference surface. Thus, the cutting block480 may receive the saw blade in the slot guides 482 to direct the sawblade relative to the patient's anatomy. The displacement sensing arm412 and related components (processor) generate a cutting depth valuethat takes into consideration the thickness of the wall of the cuttingguide/jig 480—provided the item being cut maintains contact with theinterior wall of the cutting guide/jig 480. Furthermore, thedisplacement sensing arm 412 may contact a portion of the cutting block480 that is stationary relative to the anatomy to be cut rather than theanatomy itself.

In one embodiment, the cutting guide/jig 480 is adjustable for allowingdifferent sized patient parts to be received. Also, the height, depthand width of the slot guides 482 is also adjustable for acceptingdifferent size and time type of cutting blades (e.g., reciprocating,ultrasonic, etc.) Also, guide(s) separate from or attachable to thecutting guide/jig 480 provide barriers for guiding motion of the housingof the saw in a desired cutting direction.

As shown in FIGS. 17A-C, the saw may also include a light emitter 500disposed on a distal face 30 of the saw housing 26. In this regard, thelight emitter 500 may be operable to emit light in a direction towardthe saw blade 16 when engaged with the chuck 420. As such, the lightemitter 500 may illuminate at least a portion of the saw blade 16 duringthe sawing operation to improve visibility of the medium being sawed.The light emitter 500 may include a light source such as, for example,an incandescent bulb, a light emitting diode (LED), a laser source, orother light source known in the art. Alternatively, a light source maybe disposed remotely from the light emitter 500 and the light may betransmitted from the remote light source to the light emitter 500 usingoptical elements such as fiber optics or the like. It may further beappreciated that a light emitter 500 like the one shown in theaccompanying figures may be provided with other types of surgicalinstruments without limitations. For example, a light emitter 500 of thetype described herein may be provided with other types of saws, saws, orother surgical tools. Accordingly, the light emitter 500 may beappropriately disposed relative to the surgical field so as to directlight from the light emitter 500 toward the interface of the surgicaltool with the portion of the surgical field contacted by the surgicaltool.

The light emitter 500 may be selectively operated or may be operatedwhen the saw 50 is operated. In this regard, the light emitter 500 maybe selectively toggled on and off or may include different levels ofintensity. The selector for the light emitter 500 may be at thecontroller housing 146 (e.g., a selectable option on the display 152).The light emitter 500 may also be activated upon activation of the saw50. Additionally, the operation of the light emitter 500 may beselectable between operation with the saw 500 and selective toggling ofthe light emitter 500.

In a further embodiment, the light emitter 500 may be adapted for usewith any appropriate surgical instrument. In this regard, furtherexamples of surgical instruments are shown in FIGS. 17A-C, respectively.For example, in FIG. 17A, a burr grinder 600A is shown, in FIG. 17B, asecond sagittal saw 600B is shown with a first grip embodiment, and inFIG. 17C, a third sagittal saw 600C is shown with a second gripembodiment. In FIG. 17A, the burr grinder 600A may include an instrumentworking portion comprising a rotatable burr grinding bit 610. In thisregard, the burr grinding bit 610 may be contactable with the patient toperform a grinding operation. The burr grinder 600A may also include oneor more light emitters 500. As may be appreciated, the light emitters500 may be disposed on a distal face 620 of the burr grinder 600A suchthat the light emitters 500 may be operable to emit light in a directiontoward the patient when the burr grinding bit 610 is in contact with thepatient. That is, the light emitter 500 may act to illuminate a surgicalfield in which the burr grinder 600A is employed. In the case of aplurality of light emitters 500, the light emitters may be spacedequally about a portion of the distal face 620 surrounding the workingportion of the burr grinder 600A. The light emitters 500 may be disposedwithin a housing of the burr grinder 600A such that the light emitters500 may be protected from environmental elements (e.g., fluid or thelike) that may be present when the burr grinder 600A is in use. As such,the light emitters 500 may include or be disposed behind a transparentor translucent shield 630 that may protect the light emitters 500 and/orlight source associated with the light emitters 500 from suchenvironmental elements. The light emitters 500 shown in FIG. 17A may beoperated according to any of the foregoing discussion regarding thelight emitters 500 described above.

Furthermore, with further reference to FIGS. 17B and 17C, it may beappreciated that the light emitters 500 may be provided in connectionwith other surgical instruments. For instance, in FIG. 17B, a sagittalsaw 600B with a first grip embodiment (i.e., a pistol grip style grip)is shown. In this regard, it may be appreciated that a sagittal sawblade 612 may be provided as the working portion of the sagittal saw600B. As such, the sagittal saw blade 612 may be reciprocated such thatcontact of the distal portion of the sagittal saw blade 612 may act tocut anatomy of the patient. As such, the light emitters 500 may bedisposed on a distal face of the sagittal saw 600B such that the lightemitters 500 may emit light toward the patient when the sagittal sawblade 612 contacts the patient in a cutting operation. Further still,FIG. 17C shows another embodiment of a sagittal saw 600C with a secondgrip embodiment. As may be appreciated, the light emitters 500 of thesagittal saw 600C may be disposed about the sagittal saw blade 612 in amanner as described above with respect to the burr grinder 600A.

With further reference to FIGS. 18-21C, an embodiment of a saw 700 thatmay also include a measurement system 400 for the measurement of thedisplacement of the leading edge 16 a of the saw blade 16 when advancedinto a medium. In this regard, the saw 700 may include a displacementsensing arm 412 that extends from a saw housing 26 in a manner similarto that described above. With further reference to FIGS. 19 and 20, bothof which depict internal components disposed within the saw housing 26,the saw 700 may include a displacement sensor 410. Specifically, thedisplacement sensor 410 may be a digital encoder 720 that is operativeto output a signal representative of the displacement of thedisplacement sensing arm 412 with respect to the leading edge 16 a ofthe saw blade 16.

In this regard, the proximal end 418 of the displacement sensing arm 412may extend into the housing 26 of the drill 700. Specifically, theproximal end 418 of the displacement sensing arm 412 may contact ashuttle 710 that is slideably engaged with a plurality of rails 712extending in a direction parallel to the cutting direction 120 of thesaw blade 16. The shuttle 710 may further be engaged with a belt 714.The belt 714 may be disposed about a plurality of gear hubs 716 a and716 b. In this regard, the shuttle 710 may engage a point on the belt714 such that as the shuttle 710 moves in sliding engagement along therails 712, the belt 714 imparts rotational motion to the gear hubs 716 aand 716 b.

The gear hub 716 b may be fixed on a shaft 718 that extends into thedigital encoder 720. In this regard, rotation of the shaft 718 may besensed by the digital encoder 720 and transformed into a correspondingdisplacement signal associated with the movement of the shuttle 710 whenmoved by the displacement sensing arm 412. The shuttle 710 may be biasedto a distal position.

Furthermore, the distal portion 414 of the displacement sensing arm 412may engage a bushing 452 as described above. In this regard, the bushing452 may be engaged with the saw blade 16. Specifically, the bushing 452may include a post 732 extending through an aperture 730 in the sawblade 16. Specifically, the post 732 may extend between a first portion734 of the bushing 452 on a first side of the saw blade 16 and thesecond portion 736 of the bushing 452 on a second side of the saw blade16 opposite the first side of the saw blade 16. In this regard, thebushing 452 may be captive relative to the saw blade 16 such that thebushing 452 may move with respect to the confines of the aperture 730 asthe post 732 may constrain the bushing 452 within the aperture 730. Thebushing 452 may include an engagement portion 738 that engages thedistal portion 414 of the displacement sensing arm 412. Specifically,the engagement portion 738 may comprise a snap interface such that theengagement portion 738 snaps onto and is engageable with the distalportion 414 corresponding movement therewith. Thus, as may beappreciated, the bushing 452 may include a reference surface for 60 thatis alignable with the distal edge 16 a to define a reference pointrelative to the distal edge 16 a is described above.

Furthermore, it may be appreciated that the aperture 730 in the sawblade 16 may generally be tapered or fan shaped such that the apertureextends across the greater lateral extent of the saw blade 16 towardsthe distal end thereof and converges to a lesser lateral extent of thesaw blade 16 as the aperture extends proximally. This may be provided toaccount for the greater reciprocal distance traveled by the saw blade atthe distal end thereof such that as the bushing 452 moved relative tothe saw blade 16 in a proximal direction, the corresponding relativemovement between the bushing 452 and saw blade 16 may be reduced giventhe relatively shorter stroke of the oscillations of the saw blade 16 ata proximal location.

In any regard, the bushing 452, once engaged with the displacementsensing arm 412 may undergo corresponding relative movement therewith.As such, when the saw blade 16 is advanced into a medium, the referenceedge 460 of the bushing 452 may move relative to the leading edge 16 aof the saw blade as the saw blade 16 is advanced during a sawingoperation as described above. In turn, the relative movement between thebushing 452 and the leading edge of the saw blade 16 a may be detectedby the digital encoder 720 as the displacement sensing arm 412 displacesthe shuttle 710 along the rails 712, thus turning the belt 714 on thegear hubs 716 a and 716 b that is detectable by the digital encoder 720.

FIG. 21A depicts the chuck 420 of the saw 700 without a saw blade 16disposed relative thereto. As may be appreciated, a lever 740 may beprovided relative the chuck 420. The lever 470 may be in operativecommunication with a clamping element 742 disposed within a receivingwindow 744 of the chuck 420. In this regard, with further reference toFIG. 21B, as a saw blade assembly 60 including a bushing 452 and the sawblade 16 is advanced relative to the chuck 420, the lever 740 may bedisplaced, thereby displacing the clamping element 742 and allowing theshank 744 of the saw blade 16 to be received in the receiving window 744the chuck 420. Upon return of the lever 742 to a home position, theclamping element 742 may clampingly engage the shank 744 of the sawblade 16. Furthermore, the engagement portion 738 of the bushing 452 maybe advanced relative to the proximal end 414 of the displacement sensingarm 412 for engagement there with when the shank 744 is engaged by thechuck 420.

Furthermore, as described above, the saw blade assembly 60 for use inthe embodiment of the saw 700 depicted in FIGS. 18-21C may include adestructible portion that prevents or use of the saw blade assembly 60upon cleaning thereof. In this regard, for purposes of patient safety orthe like, the saw blade assembly 60 may be a one-time use item such thatattempted reuse after a cleaning operation may prevent engagement of thesaw blade assembly 60 with the saw 700. Specifically, the bushing 452may comprise a destructible portion that is destroyed upon undergoingcleaning operation and the manner described above. Specifically, thepost 732 may be destroyed upon undergoing a cleaning operation such thatthe first portion 734 and second portion 736 may be disassociated suchthat there are no longer maintained within the aperture 730 of the sawblade 16.

Those skilled in the art will appreciate that changes could be made tothe embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1.-27. (canceled)
 28. A saw blade assembly for use in a medical saw forsingle use applications, the saw blade comprising: a cutting edgedisposed at a distal end of the saw blade; a shank disposed adjacent toa proximal end of the saw blade; a blade member extending between thedistal end and the proximal end; a bushing configured to be locatedadjacent to at least a portion of the blade member, wherein the bushingis constrainedly moveable relative to the blade member in a directioncorresponding to the length of the blade member; and a destructibleportion that is at least partially destructible during a cleaningprocess.
 29. The saw blade assembly according to claim 1, wherein thedestructible portion is meltable.
 30. The saw blade assembly accordingto claim 29, wherein a melting temperature of the destructible portionis greater than an operating temperature of the saw blade and less thanan autoclave temperature.
 31. The saw blade assembly according to claim30, wherein the melting temperature of the destructible portion is notless than about 60° C. and not greater than about 110° C.
 32. The sawblade assembly according to claim 28, wherein the destructible portioncomprises a proximal end portion of the shank.
 33. The saw bladeassembly according to claim 32, wherein the destructible portioncomprises at least a portion of an engagement feature for engagement ofthe shank by a chuck.
 34. The saw blade assembly according to claim 33,wherein the destructible portion, after having been exposed to acleaning process, is not registerable with respect to the chuck.
 35. Thesaw blade assembly according to claim 28, wherein the destructibleportion comprises a portion of the bushing.
 36. The saw blade assemblyaccording to claim 35, wherein the destructible portion comprises anengagement portion of the bushing.
 37. The saw blade assembly accordingto claim 35, wherein the destructible portion comprises a portion of thebushing constraining the bushing to the blade member, wherein upondestruction of the destructible portion, the bushing is not constrainedto the blade member.
 38. A method for a saw blade assembly for use in amedical saw for single use applications, comprising: exposing the sawblade to a cleaning process; and degrading at least a portion of adestructible portion of the saw blade assembly in response to theexposing.
 39. The method according to claim 38, wherein the exposingcomprises autoclaving the saw blade.
 40. The method according to claim39, wherein the degrading comprises melting at least a portion of thedestructible portion in response to the autoclaving.
 42. The methodaccording to claim 40, wherein the melting occurs at a temperature ofnot less than about 60° C. and not greater than about 110° C.
 43. Themethod according to claim 38, wherein the exposing comprises applying acleaning chemical to the saw blade assembly and the degrading comprisesremoving of at least a portion of the destructible portion in responseto applying the cleaning chemical.
 44. The method according to claim 38,wherein the degrading results in changing a shape of a shank of the sawblade.
 45. The method according to claim 44, wherein the degradingcomprises removing at least a portion of the destructible portion at ashank of the saw blade.
 46. The method according to claim 45, whereinthe portion of the destructible portion removed comprises at least aportion of an engagement feature for engagement of the shank by a chuck.47. The method according to claim 40, wherein the degrading results inreducing the registration of the shank with respect to a chuck of a saw.48. The method according to claim 38 wherein the degrading comprisesremoving at least a portion of the destructible portion at the bushing.49. The method according to claim 48, wherein the degrading comprisesdestroying an engagement portion of the bushing.
 50. The methodaccording to claim 49, wherein the degrading comprises destroying aportion of the bushing constraining the bushing to the blade member,wherein upon the destroying of the destructible portion, the bushing isnot constrained to the blade member. 51.-93. (canceled)